2,026 research outputs found
Neutrino mass constraint from CMB and its degeneracy with other cosmological parameters
We show that the cosmic microwave background (CMB) data of WMAP can give
subelectronvolt limit on the neutrino mass: m_nu < 0.63 eV (95% CL). We also
investigate its degeneracy with other cosmological parameters. In particular,
we show the Hubble constant derived from the WMAP data decreases considerably
when the neutrino mass is a few times 0.1 eV.Comment: 3 pages, 2 figures, prepared for the TAUP2007 Proceeding
Measuring the Topology of the Universe
Observations of microwave background fluctuations can yield information not
only about the geometry of the universe, but potentially about the topology of
the universe. If the universe is negatively curved, then the characteristic
scale for the topology of the universe is the curvature radius. Thus, if we are
seeing the effects of the geometry of the universe, we can hope to soon see
signatures of the topology of the universe. The cleanest signature of the
topology of the universe is written on the microwave sky: there should be
thousands of pairs of matched circles. These circles can be used to determine
the precise topology and volume of the universe. Since we see hundreds of
slices through the fundamental domain of the universe, we can use the microwave
observations to reconstruct the initial conditions of the entire universe on
the scale of a few Megaparsecs.Comment: 11 pages, LaTex, Talk at NAS Cosmology Conference, Irvine, CA, March
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A strong first order phase transition in the UMSSM
In this work, the electroweak phase transition (EWPT) strength has been
investigated within the extended Minimal Supersymmetric Standard Model
(UMSSM) without introducing any exotic fields. We found that the EWPT could be
strongly first order for reasonable values of the lightest Higgs and neutralino
masses.Comment: talk presented in PASCOS2010, Valencia, Spain from 19-23 Jul. 201
Searching for Oscillations in the Primordial Power Spectrum: Perturbative Approach (Paper I)
In this first of two papers, we present a new method for searching for
oscillatory features in the primordial power spectrum. A wide variety of models
predict these features in one of two different flavors: logarithmically spaced
oscillations and linearly spaced oscillations. The proposed method treats the
oscillations as perturbations on top of the scale-invariant power spectrum,
allowing us to vary all cosmological parameters. This perturbative approach
reduces the computational requirements for the search as the transfer functions
and their derivatives can be precomputed. We show that the most significant
degeneracy in the analysis is between the distance to last scattering and the
overall amplitude at low frequencies. For models with logarithmic oscillations,
this degeneracy leads to an uncertainty in the phase. For linear spaced
oscillations, it affects the frequency of the oscillations. In this first of
two papers, we test our code on simulated Planck-like data, and show we are
able to recover fiducial input oscillations with an amplitude of a few times
order 10^{-2}. We apply the code to WMAP9-year data and confirm the existence
of two intriguing resonant frequencies for log spaced oscillations. For linear
spaced oscillations we find a single resonance peak. We use numerical
simulations to assess the significance of these features and conclude that the
data do not provide compelling evidence for the existence of oscillatory
features in the primordial spectrum.Comment: 13 pages, 22 figures. Paper 1 of 2. Fixed typos, added reference
Tuning the stochastic background of gravitational waves using the WMAP data
The cosmological bound of the stochastic background of gravitational waves is
analyzed with the aid of the WMAP data, differently from lots of works in
literature, where the old COBE data were used. From our analysis, it will
result that the WMAP bounds on the energy spectrum and on the characteristic
amplitude of the stochastic background of gravitational waves are greater than
the COBE ones, but they are also far below frequencies of the earth-based
antennas band. At the end of this letter a lower bound for the integration time
of a potential detection with advanced LIGO is released and compared with the
previous one arising from the old COBE data. Even if the new lower bound is
minor than the previous one, it results very long, thus for a possible
detection we hope in the LISA interferometer and in a further growth in the
sensitivity of advanced projects.Comment: 9 pages, 2 figures, published in Modern Physics Letters A. arXiv
admin note: substantial text overlap with arXiv:0901.119
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